Chapter 3 – The Dynamic EarthSection 1: The Geosphere

1. Describe the composition & structure of the Earth

2. Describe the Earth’s tectonic plates3. Explain the main cause of earthquakes & their

effects4. Identify the relationship between volcanic

eruptions & climate change5. Describe how wind & water alter the Earth’s

surface

The Earth as a System

• Earth consists of rock, air, water, & living things that interact with each other

• Divided into 4 parts:WATER

LIVING THINGS

ROCK

AIR

The Earth as a System• Geosphere– Solid portion consisting of rock– Extends from center of core to surface of crust

• Atmosphere– Mixture of gases– Most found in first 30 km above Earth’s surface

• Hydroshpere– All water on or near surface– Most is oceans

• Biosphere – Where life exists– Extends from 9 km above surface to bottom of ocean

Discovering Earth’s Interior• Seismic waves used

to study interior of Earth

• Seismic waves– Travel through

Earth’s interior during earthquakes

– Altered by type of material they move

– Changes in speed & direction measured when passing through different layers

Earthquake

Seismic wave

Composition of the Earth

• Divided into three layers based on composition – Crust– Mantle – Core

• layers become progressively denser toward the center

Crust

Mantle

Core

Crust• Thin, outermost layer – 5 to 8 km beneath oceans– 20 to 70 km beneath

continents

• Solid, brittle • Composed of lightweight

elements• Makes up less that 1% of

Earth’s mass

Mantle• Layer between crust &

core• Composed of rock with

medium density• Contains iron-rich

minerals• Makes up 64% of

Earth’s mass• Approximately 2900 km

thick

Core• Innermost layer– Liquid outer core• Super-heated molten lava• Composed of liquid nickel

& iron– Solid inner core• Sphere of solid nickel &

iron

• Consists of densest elements

• Radius approximately 3400 km

Solid inner core

The Structure of the Earth

• Divided into 5 layers based on the physical properties

Lithosphere

Asthenosphere

Mesosphere

Outer CoreInner Core

Lithosphere• Composes crust &

upper part of mantle

– 15-300 km thick (9-185 mi)

• Divided into large pieces called tectonic plates– May be oceanic or

continental– Slide on fluid portion

of mantle– Movement can cause

earthquakes

Asthenosphere

• Beneath lithosphere– 250 km thick (150 mi)

• Solid, plastic-like material of mantle– Made of rock that

flows– Due to temperature &

pressure• Allows for movement

of tectonic plates

Mesophere

• Lower part of mantle

• More solid & rigid than asthenosphere due to increased pressure – Can’t flow

Lithosphere

Asthenosphere

Mesosphere

Outer CoreInner Core

Outer Core• Super-heated molten

lava– Composed of liquid nickel

& iron– 4000 to 9000 °F

• Source of Earth’s magnetic field– Creates protective bubble– Deflects Sun’s solar winds

Inner Core

• Solid ball• Composed of nickel

& iron• 9000 °F &

45,000,000 psi• Rotates in liquid

outer core

Plate Tectonics

• Large, irregularly shaped slabs of rock• Composed of oceanic & continental

lithosphere– Continental rocks• Lightweight minerals (quartz, feldspar)• Thicker crust

– Oceanic rocks• Heavier, denser basltic rocks• Thinner crust

Major & Minor Tectonic Plates

Plates move in different directions and speeds, thus crash together, pull apart or side swipe each other like cars in a demolition derby

Plate Boundaries• Most geologic activity occurs where plates meet or

divide (called boundaries)• Movement of plates creates 3 types of tectonic

boundaries– Convergent – plates collide, move into one another– Divergent – plates move apart– Transform – plates move sideways in relation to one

another• Movement of tectonic plates causes– Mountain formation– Earthquakes– Volcanic eruptions

Plate Tectonics and Mountain Formation

• Plates collide, crust thickens

• Rocks break & buckle– Continental plate folds

into huge mountain – Oceanic plate forms

trench• Examples– Rocky mountains (N.

America)– Himalaya mountains

(Central Asia

Earthquakes• Faults – breaks in Earth’s

crust where plates slide past each other

• Rocks under stress break off triggering ground vibrations - called earthquakes

• Magnitude (Richter Scale)– Measure of energy released– 2.0 – smallest felt– 9.5 – largest recorded– Increase of 1 whole number

= 31.7 times more energy

Where Earthquakes Occur

Most occur at or near plate boundaries

Earthquake Hazard• Earthquake hazard level determined by past &

present seismic activity• Hazards (effects) include– Ground shaking (building damage/settling of ground

beneath to different level)– Ground displacement – Flooding (breakage of levies, dams, Tsunamis)– Fire (broken gas & power lines)

• Human hazards due to man-made structures– Being crushed, buried or burned or drowning

• National Hazards Maps used by cities, counties & local governments to update & create more stringent building codes

Volcanoes• Mountains built from

magma (molten rock)• Magma rises to

surface from interior• Most common at

convergent or divergent plate boundaries

• Can occur on land or in oceans

Block between separating faults cracks, drops into asthenosphere forming a rift. Magma seeps upward to fill in crack

Volcanoes: The Ring of Fire

• Majority of active volcanoes on land located along tectonic plate surrounding the Pacific Ocean

Pacific Plate

North American PlateEurasian Plate

Antarctic Plate

South American Plate

Australian Plate

Local Effects of Volcanic Eruptions

• Clouds of hot ash, dust, & gases flow down the slopes of volcanoes searing anything in its path– Obscures sunlight, killing plants & animals

• Volcanic ash mixes with water producing mudflows– Water contamination– Land contamination

• Collapse of buildings, burying of crops, & damage to vehicle engines due to falling ash

Global Effects of Volcanic Eruptions

• Can cause changes in Earth’s climate• Ash & sulfur-rich gases reach upper

atmosphere & reduce sunlight reaching Earth’s surface

• Reduction in sunlight reduces average global temperatures

Erosion• Process resulting in materials of the Earth’s surface

being loosened, dissolved or worn away & transported from one place to another by natural agents such as wind, water, ice or gravity

• Water erosion– Rivers carve deep canyons or gorges into bedrock– Depositing of dust, pebbles, rocks forms new land areas– Oceans erode coastlines

• Wind erosion– Removal of most fertile part of soil lowering soil

productivity– Creates sand dunes